The present invention relates to improvements in apparatus for folding paper sheets or the like. More particularly, the invention relates to improvements in apparatus of the type wherein successive sheets are folded by a wedge-like folding device which extends into a complementary groove of a conveyor for transport of successive sheets between the conveyor and the folding device.
German Offenlegungsschrift No. 2,450,113 discloses a sheet folding apparatus wherein the outer side of an endless conveyor is formed with a longitudinally extending groove which moves past a wedge-like male folding member. The sheets to be folded are placed onto or are otherwise caused to adhere to the outer side of the conveyor so that each sheet is folded during transport past the male folding member. The apparatus which is disclosed in the aforementioned Offenlegungsschrift further comprises a magazine for a stack of unfolded sheets and a feeding mechanism which delivers successive sheets of the stack to the grooved conveyor. Prior to delivering a sheet to the grooved conveyor, the feeding mechanism provides such sheet with a crease to facilitate folding of successive sheets during travel past the male folding member. The conveyor is a first endless chain conveyor which carries a series of grooved matrices and includes an elongated straight stretch or reach for transport of successive matrices (in a common plane) past the male folding member. The sheets to be folded are supported by or attracted to the exposed sides of the matrices. The male folding member is a composite member including a row of wedges which are secured to a second endless chain conveyor. A stretch of the second chain conveyor is parallel to the aforementioned stretch of the first chain conveyor, and successive wedges of the male folding member travel in the same direction as the matrices on the first chain conveyor. As a rule, the matrices cooperate with the wedges of the male folding member to effect a partial folding of successive sheets; final folding takes place during transport of partially folded sheets between one or more pairs of folding or squeezing rollers.
A drawback of the just described apparatus is that the aforementioned straight stretches of the chain conveyors are not supported or propped from within. Therefore, and especially if the apparatus is operated at a high speed, the chain conveyors are likely to vibrate which entails undesirable and often pronounced shifting of sheets, especially of relatively thin sheets. Consequently, the line along which the wedges of the second chain conveyor fold the sheets during travel of sheets with the straight stretch of the first chain conveyor; in most instances, does not coincide with the line along which the sheet is creased during delivery from the magazine to the first chain conveyor.